(a) Field of the Invention
The present invention relates to a thin film transistor (TFT) array substrate for a liquid crystal display and, more particularly, to a TFT array substrate having with repair lines.
(b) Description of the Related Art
Generally, liquid crystal displays are structured with a color filter substrate with a common electrode and color filters, a TFT array substrate with TFTs and pixel electrodes, and a liquid crystal sandwiched between the substrates. In operation, different voltages are applied to the common electrode and the pixel electrodes to form electric fields, and under the application of the electric fields, the molecular orientation of the liquid crystal changes. This controls light transmission and displays pictorial images on the screen.
The TFTs are connected to the pixel electrodes individually in order to switch the voltage applied to each pixel electrode.
Gate lines for transmitting scanning signals to the TFTs, and data lines for transmitting pictorial image signals to the TFTs are formed at the TFT array substrate. Such gate and data lines are easy to break or to be disconnected during the device fabricating process. In order to repair such a breakage or disconnection, repair lines are usually provided at the TFT array substrate.
Conventionally, one or two repair lines are formed at the target data lines or gate lines such that they cross both end portions of the data or gate lines. The repair lines are interconnected via lines formed at tape carrier packages (TCPs) and at a printed circuit board (PCB).
In the TFT array substrate with such repair lines, when lines (for example, data lines) are broken, a laser is irradiated to the crossed portion between the broken line and the repair line and both sides of the broken line are short-circuited by way of the repair line. In this way, pictorial image signals can be transmitted to the disconnected side of the data line via the repair line.
However, when one or two repair lines cross all of the gate lines or data lines, four broken lines may be repaired at most.
In order to repair more broken lines, it has been suggested that the lines connected to one driving integrated circuit (IC) be packaged into one block, and that a separate repair line be formed for each block.
However, such a technique involves several shortcomings.
First, in the usual TCPs, it is difficult to form as many pads as the number of repair lines. Furthermore, as the number of pads increases, the length of the TCPs for the gate driving IC should increase to be connected to the underlying repair lines. Consequently, TCPs having a special structure would be required, resulting in increased production cost. In addition, either as many interconnection lines for the repair lines should be formed at the PCB as the number of driving ICs, or twice as many. Therefore, the volume of the PCB would be increased, resulting in a larger device size.